The prior art of motor-powered depilatory devices using springs for removing skin hair is based on a well-known operational concept of an early mechanical device disclosed in Swiss Pat. 268,696 to Fischer. This hand-operated device uses an arched coil spring to trap and pluck hair between its loops as it rolls over the skin.
Other hand-operated coil spring designs are disclosed in the group including Swiss Patent 179,261 to Macioce, U.S. Pat. No. 2,458,911 to Kerr, U.S. Pat. No. 2,486,616 to Schubiger, British Patent 203,970 to Davis, U.S. Pat. No. 1,743,590 to Binz, and U.S. Pat. No. 1,232,617 to Shipp. There vary in the mechanical arrangements for stretching the spring and engaging the hair between coil spring loops before it is trapped upon closure of the stretched spring.
U.S. Pat. No. 4,079,741 to Daar et al. discloses a single tension spring disposed parallel to the skin and arranged to be stretched and compressed so as to pluck hairs trapped between its loops. The overall design is complicated and expensive.
An arched helical spring provided with high speed rotational motion for opening and closing the loops is provided in U.S. Pat. No. 4,524,772 to Daar et al. U.S. Pat. Nos. 4,726,375 and 4,807,624 to Gross et al. disclose a rubber hair-plucking element with partially circumferential slits or rubber discs for trapping and plucking skin hair.
These patents are all based on the concept of rotating the coil spring or slits near the skin to enable hairs to become trapped, but they have a tendency to "wind" while slowly developing sufficient hair-pulling tension, and this creates additional discomfort in use of these devices. In addition, with the spring designs, the contact with the hair is point-like, increasing the likelihood that hair will be pinched and torn, but not plucked.
U.S. Pat. No. 1,923,415 to Bingham discloses a plurality of rotatable discs arranged to be bent one or more times toward each other at a point during each revolution, causing them to pluck bird feathers. This design is not applicable to hair plucking as it is complicated, expensive to manufacture, and inefficient.
French Patent 1,017,490 to Bachofen discloses a bird feather plucking device using a set of rotatable discs, each disc having a curved surface area, and being arranged to be bent toward one another at a point during each revolution. Again, this is a complicated, and inefficient design.
Another device for removing bird feathers is disclosed in French Patent 1,123,971 to Jadoul, based on a plurality of rotatable discs arranged to be bent toward one another at a point during each revolution. Again, this is an inefficient design.
Still another poultry feather plucking device is disclosed in U.S. Pat. No. 2,496,223 to Lanzisera, based on the use of a helical spring which rotates on one side of a grid, such that feathers which project through the grid are grasped between loops of the spring and are plucked. This design allows only one plucking action per revolution of the spring, besides being complicated and expensive to manufacture.
In general, the spring and disc designs available for feather plucking are not applicable to hair plucking, due to their size, complicated construction and inefficient operation.
Another disc design is disclosed in U.S. Pat. No. 2,900,661 to Schnell, wherein a pair of discs rotate at a large angle to each other and converge at a contact point whereat hairs are plucked. The large size of this design makes it inefficient since only a few discs can be located within a given space, and the inflexible discs tend to cut the hair, not pluck it.
In U.S. Pat. No. 4,575,902 to Alazet, there is disclosed a depilatory device comprising a series of adjacent, closely-spaced hair-plucking discs driven by an electric motor. In one embodiment, the discs are periodically deformed during rotation so as to trap hair between them as they are pressed together. This design very similar to the Jadoul patent described earlier, and is similarly inefficient since the discs close only once per rotation, limiting plucking action to a short time interval. Also, it is not feasible to achieve closure of the large number of discs by deformation since the cumulative spacing is too great.
In the second embodiment described in the Alazet patent, a pair of movable hair-gripping combs are positioned between adjacent discs to provide hair plucking when they are applied against the discs. Each of the combs is movable on its own shaft and its area covers only an angular sector of the disc against which it is applied, so that only a partial disc area is effective for plucking of hair. The disclosure suggests that more than two combs may be used to increase the effective disc area used for plucking, but this would require additional movable shafts and cams, which cannot be achieved within a limited space without further complicating the construction and operation.
A design similar to Alazet is marketed by Calor under the tradename "Caresse" and uses two cam-operated shafts for moving a set of movable tweezers against a set of fixed discs in one direction only, once per revolution. Another similar design is marketed by Braun under the tradename "Silkappeal" and has a plurality of moving segments closing against one another once per revolution. Both are complicated and inefficient designs.
In my previous U.S. Pat. No. 4,935,024 there is disclosed a novel coupled-disc element which reduces the "winding" phenomenon of previous designs, while reducing the painful sensation.
It would therefore be desirable to provide a power-driven depilatory device which provides efficient hair removal by increasing the number of hair plucking operations using a simplified construction.
It would also be desirable to provide a depilatory device which is simple in construction for cost-effective production, while durable in use.
Additionally, it would be desirable to provide a depilatory device which minimizes pain in relation to prior art spring designs and achieves greater efficiency with respect to prior art discs designs, while being simple to manufacture, use and maintain.